Background Since the early ‘80s, the pulsed dye laser has been the standard treatment tool for non‐invasive port wine stain (PWS) removal. In the last three decades, a considerable amount of research has been conducted to improve clinical outcomes, given that a fraction of PWS patients proved recalcitrant to laser treatment. Whether this research actually led to increased therapeutic efficacy has not been systematically investigated. Objective To analyse therapeutic efficacy in PWS patients globally from 1986 to date. Methods PubMed was searched for all available PWS trials. Studies with a quartile percentage improvement scale were included, analysed and plotted chronologically. Treatment and patient characteristics were extracted. A mean clearance per study was calculated and plotted. A 5‐study simple moving average was co‐plotted to portray the trend in mean clearance over time. The data were separately analysed for multiple treatment sessions in previously untreated patients. Results Sixty‐five studies were included (24.3% of eligible studies) comprising 6207 PWS patients. Of all patients, 21% achieved 75–100% clearance. Although a few studies reported remarkably good outcomes in a subset of carefully selected patients, there was no upward trend over time in mean clearance. Conclusion The efficacy of PWS therapy has not improved in the past decades, despite numerous technical innovations and pharmacological interventions. With an unwavering patient demand for better outcomes, the need for development and implementation of novel therapeutic strategies to clear all PWS is as valid today as it was 30 years ago.

Background Valid and reliable outcome measures are needed to determine and compare treatment results of port wine stain (PWS) studies. Besides, uniformity in outcome measures is crucial to enable inter-study comparisons and meta-analyses. This study aimed to assess the heterogeneity in reported PWS outcome measures by mapping the (clinical) outcome measures currently used in prospective PWS studies. Methods OVID MEDLINE, OVID Embase, and CENTRAL were searched for prospective PWS studies published from 2005 to May 2020. Interventional studies with a clinical efficacy assessment were included. Two reviewers independently evaluated methodological quality using a modified Downs and Black checklist. Results In total, 85 studies comprising 3,310 patients were included in which 94 clinician/observerreported clinical efficacy assessments had been performed using 46 different scoring systems. Eighty-one-studies employed a global assessment of PWS appearance/improvement, of which-82% was expressed as percentage improvement and categorized in 26 different scoring systems. A wide variety of other global and multi-item scoring systems was identified. As a result of outcome heterogeneity and insufficient data reporting, only 44% of studies could be directly compared. A minority of studies included patient-reported or objective outcomes. Thirteen studies of good quality were found.

<b><i>Background:</i></b> A plethora of outcome measurement instruments (OMIs) are being used in port wine stain (PWS) studies. It is currently unclear how valid, responsive, and reliable these are. <b><i>Objectives:</i></b> The aim of this systematic review was to appraise the content validity and other measurement properties of OMIs for PWS treatment to identify the most appropriate instruments and future research priorities. <b><i>Methods:</i></b> This study was performed using the updated Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) methodology and adhered to PRISMA guidelines. Comprehensive searches in Medline and Embase were performed. Studies in which an OMI for PWS patients was developed or its measurement properties were evaluated were included. Two investigators independently extracted data and assessed the quality of included studies and instruments to perform qualitative synthesis of the evidence. <b><i>Results:</i></b> In total, 1,034 articles were screened, and 77 full-text articles were reviewed. A total of 8 studies were included that reported on 6 physician-reported OMIs of clinical improvement and 6 parent- or patient-reported OMIs of life impact, of which 3 for health-related quality of life and 1 for perceived stigmatization. Overall, the quality of OMI development was inadequate (63%) or doubtful (37%). Each instrument has undergone a very limited evaluation in PWS patients. No content validity studies were performed. The quality of evidence for content validity was very low (78%), low (15%), or moderate (7%), with sufficient comprehensibility, mostly sufficient comprehensiveness, and mixed relevance. No studies on responsiveness, minimal important change, and cross-cultural validity were retrieved. There was moderate- to very low-quality evidence for sufficient inter-rater reliability for some clinical PWS OMIs. Internal consistency and measurement error were indeterminate in all studies. <b><i>Conclusions:</i></b> There was insufficient evidence to properly guide outcome selection. Additional assessment of the measurement properties of OMIs is needed, preferentially guided by a core domain set tailored to PWS.